Do the math, measure the tire's rolling diameter, then.....
20168.115/dia = tire revs/mi
tire revs/mi*final drive ratio = rear wheel rpm
rear wheel rpm*60/tire revs/mi = mph
or to find rear wheel rpm, or motor rpm in this case since the final drive
ratio is 1:1.....
tire revs/mi*mph*final drive ratio/60 = rear wheel rpm
Assuming a 4.5" cross section (no time right now to look it up), I calculate
the dia of a 175/70 tire to be ~19.28", so hypothetically at 60mph the
motor/tires are turning at ~4414rpm, or ~13.6mph/1krpm.
Anyway, since the math pretty much jives with your measurements and my dim
memory of what my various spridgets turned at 70mph with stock gearing, it
appears at a glance that these charts are too far off to be of any practical
use. :^(
GM
----- Original Message -----
i have read that with a 4.22 rear end,
> 175/70 tires in 4th gear that there are (either, depending upon
> Paul A. or the tech section on gerard's website) 15.46 or 15.6
> mph per 1000 rpm.... this works out out 3880 rpm for 60 mph, or
> 3846, depending upon whom one believes.... :-).
>
> when i set up the tach (i'm trying to calibrate it) with a dwell
> tach set for 4 cylinder (its an OLD one, that even has the
> directions for Postive ground, and HEALEYs actually listed in
> the documentation!!!) and TIME myself thru the measured miles on
> the freeway, i show i have to turn about 4400 rpm to go one mile
> in 60 seconds..............
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